Beta-Sialon Phosphor Production for High Luminous Efficiency
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Solution Overview
Problem
Current β-SiAlON phosphors have limitations in luminous efficiency, particularly in white light-emitting diodes, as they exhibit low external and internal quantum efficiencies due to non-luminous absorption and crystal defects.
Innovation Solution
A method for producing β-SiAlON phosphors involving a baking process in a nitrogen atmosphere at 1850-2050°C, followed by heating in a noble gas atmosphere at 1300-1550°C, and a cooling process at 1200-1000°C for 20 minutes or longer, along with an acid treatment, to enhance crystallinity and reduce impurities and crystal defects, resulting in a phosphor with high diffuse reflectance and improved quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional β-SiAlON phosphors are used, then the structure is simple and manufacturing is easy, but the internal quantum efficiency is low due to non-luminous absorption and crystal defects
Solution Approach 1:
The manufacturing process is divided into distinct stages: initial sintering at 1850-2050°C in nitrogen atmosphere, followed by separate heat treatment at 1300-1550°C in noble gas atmosphere, and subsequent acid treatment. This segmentation allows each process step to be optimized independently for removing specific types of defects and impurities, thereby improving internal quantum efficiency without excessive overall complexity
Solution Approach 2:
The acid treatment step is performed as a preliminary action before final phosphor application. This preliminary treatment removes surface impurities and crystal defects that would otherwise cause non-luminous absorption, preparing the phosphor for optimal luminescent performance in the final application
2Manufacturing precision
If the cooling process is shortened to increase productivity, then the manufacturing time is reduced, but the internal quantum efficiency decreases due to retained crystal defects
Solution Approach 1:
The cooling parameters are specifically optimized: cooling at 1200-1000°C for 20 minutes or longer. This parameter change in the cooling stage enables sufficient time for crystal defect removal and ordering, improving internal quantum efficiency while minimizing impact on overall productivity through efficient temperature management
3Illumination intensity
If the Eu content is increased to enhance emission intensity, then the brightness is improved, but the non-luminous absorption increases reducing the luminous efficiency
Solution Approach 1:
The Eu content is precisely controlled within the range of 0.1 to 2% by mass. This parameter optimization ensures sufficient emission intensity while preventing excessive non-luminous absorption. The optimized composition, combined with the refined manufacturing process, achieves high luminous efficiency by balancing emission strength with minimal energy loss
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method results in β-SiAlON phosphors with increased internal quantum efficiency, reduced non-luminous absorption, and enhanced luminous efficiency, leading to improved brightness and longevity in light-emitting applications.
Implementation Method 1
β-SiAlON phosphors, which absorb blue light at a wavelength of 455 nm and emit blue-green light at a wavelength of 540 nm
Implementation Method 2
a baking process of baking a raw material powder mixture containing Si, Al, and Eu in a nitrogen atmosphere at 1850°C to 2050°C
Implementation Method 3
a cooling process of cooling the mixture having undergone the heating process at temperatures of 1200°C to 1000°C for 20 minutes or longer
Data Source
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AI summary
The present invention provides a β-SiAlON phosphor that contains a β-SiAlON represented by a general formula Si6-zAlzOzN8-z (0<z<4.2) as a matrix and Eu2+ in a form of a solid solution as an emission center, and exhibits a peak within a wavelength range from 520 to 560 nm when excited by blue light. The average diffuse reflectance of this β-SiAlON phosphor in the wavelength range from 700 to 800 nm is 90% or higher, and the diffuse reflectance in the fluorescent peak wavelength is 85% or higher.